The field of the invention relates to synchronous digital data communications.
In a synchronous data transmission system it is required that a clock signal be transmitted with the data in order to mark the location of the data bits for the receiver. The receiver will examine the string of data bits being transmitted and when the synchronous compare character is recognized, the receiving station will lock onto the transmitting station. At present this synchronization character is standard throughout industry, i. e. a hexadecimal 1,6 in ASCII code or 3,2 EBCDIC. This character is fixed or wired into the receiving and transmitting portions of the data communication apparatus thereby making it possible for any transmitter to communicate with any receiver.
However, by making this synchronous character dynamically alterable between message transmissions, the security of a data communication systems may be greatly increased. Since without this character it will be impossible, for example, for an unauthorized terminal to gain access to a remote computer's data base and extract confidential data. Therefore, by providing dynamically alterable synchronous compare characters, the overall security of a data communications systems may be significantly enhanced.